Automatic approach alarm



April 16, 1957 D. R WINTERS 2,739,282

' AUTOMATIC APPROACH ALARM Filed May 17, 1954 I 3 Sheets-Sheet l INVENTOR. pin 2256 J2. W VIZES' April 6,- 1957 D. R. WINTERS 2,789,282

AUTOMATIC APPROACH ALARM 7 File May 17;, 1954 s Sheets-Sheet 2 INVENTOR. 91/2 52 1%? Uni 7%;

April 16, 1957 D. R. WINTERS AUTOMATIC APPROACH ALARM 3 Sheets-Sheet 3 Filed May 17, 1954 INVENTOR. gANIEL P Vmrmes P XM +ATTOHMEY United States Patent AUTOMATIC APPROACH ALARM Daniel R. Winters, Lawndale, Calif., assignor to Vincent Manufacturing Corporation, Los Angeles, Calrfl, a corporation of California Application May 17, 1954, Serial No. 430,015

8 Claims. (Cl. 340-258) This application is in part a continuation of application Serial No. 309,433, filed September 13, 1952, for Automatic Approach Alarm, now abandoned.

It is a principal object of the present invention to provide an alarm of the type which may be used on boom and crane equipment to automatically give an alarm when the boom equipment approaches closer than a pre-determined distance to energized power lines.

It is a further object of the present invention to provide safety features in an alarm of the foregoing type which will warn the boom or crane operator in the event of failure of certain vital components of said alarm.

Other objects of the present invention are to provide an automatic approach alarm bearing the above objects in mind which is of a simplified construction, inexpensive to manufacture, has a minimum number of parts, is easy to operate and is eflicient in operation.

For other objects and for a better understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawing, in which:

Fig. 1 is an electrical circuit diagram illustrating the control box circuit in the preferred form of my invention;

Fig. 2 is a side elevational view of a crane and showing the present invention applied thereto; and

Fig. 3 is a schematic view of a modified form of the invention.

While a preferred form of the invention will be described as applied to a crane or boom, it will be recognized that this application is purely illustrative and that actually the invention has many and varied other uses, as will be apparent to those skilled in the art.

The invention as disclosed in Figs. 1 and 2 Referring now to Fig. 2, reference numeral 14 indicates an antenna of any suitable size which is mounted on and a suitably insulated from the boom of the crane. A lead-in wire 12 is electrically connected to the antenna 14 and this lead-in wire 12 may be spaced from the boom by insulated stand-ofis such as 15. chored to one end of a strain insulator 13 and is provided with a connector 11 at its end remote from the antenna. The connector 11 is adapted to be received by an antenna terminal (Fig. 1) located in a control unit C (Fig. 2).

A connecting element such as 16 connects the lower end of the strain insulator 13 to a lever 17 of an antenna interlock switch 18, which is normally spring mounted and urged to anopen position but which is held in its closed position by the relatively taut portion of the leadin wire 12 intermediate the switch 18 and the antenna 14. It will be appreciated that if lead-in wire 12 should break intermediate switch 18 and antenna 14, the switch is at once allowed to return to its normal'position; the advantages of this feature will be recognized from the further description which follows.

Referring now particularly to Fig. 1, antenna terminal Lead-in wire 12 is an- 10 is connected to one end of a resistor 19 the other end of which is connected to a common ground such as for example the control box chassis. A sliding contact 26 is connected to the control grid 21 of a tetrode 22 which is supplied with voltage for its screen grid 23 by a voltage divider comprising resistors 24 and 25, which are connected in series across a plate voltage supply B-1- and ground. Resistor 26, which is connected at one end to B|-, supplies voltage for the plate 27. The output of tube 22 is coupled to the input of a tetrode 28 by means of a coupling capacitor 29, which is connected to the grid 30 of tube 28. The input voltage to tube 28 is developed across resistor 31 which is connected between grid 30 and ground. The coil 32 of a relay having normally closed contacts 33 is connected between plate 34 and screen grid 39. The upper one of the contacts 33 is connected to contact a of a receptacle R, while the lower one of the contacts 33 is connected to one side of the filament of tube 28 and also to the stationary contact 35 of a single pole single-throw switch 36 the movable contact 37 of which is connected to a source of filament voltage for tubes 22, 28.

It will be observed that receptacle R is provided with further contacts I), c and 4, which are respectively connected to ground, to B+ and to screen grid 39. A plug P i provided for engaging receptacle R and this plug has contacts a, b, c and d which connect respectively with contacts a, b, c and d on receptacle R. An alarm device such as bell B is connected across contacts a and b, while the contacts of the normally open switch 18 are connected across contacts c' and d of plug P.

It will be observed also that the filaments of tubes 22 and 23 are connected in series.

' When switch 36 is turned on, the filament circuits are energized and the plate voltage is applied. This results in current flow through each of the tubes. When current flows through tube 28, and therefore through coil 32, the coil 32 becomes energized whereupon the relay contacts 33 separate or open. On inspection of the circuit, it will be apparent that when switch 36 is initially closed, an energizing circuit will be completed for the alarm bell B, from ground, through contacts a and b of receptacle R, through relay contacts 33 (which are momentarily closed until the tube 28 warms up), and through switch 36 to the A battery supplying filament voltage. The safety features of this arrangement should be readily apparent, since if either of the filaments of tubes 22, 28 burn out, there will be no filament voltage available for either tube, and in the absence of space current flow through tube 28, relay coil 32 will be deenergized. If the battery supplying the plate voltage be comes weak, again there will be either an inadequate space current or no space current at all through tube 28 and again relay coil 32 will be deenergized. In this deenergized condition, of course, contacts 32 are closed and alarm bell B sounds.

If the lead-in Wire 12 intermediate switch 18 and antenna breaks, the contacts of switch 18 will open and this will remove plate voltage from plate 34 of tube 28, whereupon contacts 33 are again closed, and alarm bell B sounds.

It will be noted that it is quite important that the battery supplying bell voltage, which in Fig. l is the same battery as the one supplying filament voltage, be in good condition so that it can energize the bell B. From what has been said hereinbefore it will be clear that the bell will ring each time the switch 36 is closed, thus giving the necessary indication that the bell voltage battery is in proper operative condition.

If desired, a separate bell voltage may be provided, in addition to a filament battery. Such a separate bell 3. voltage may conveniently be connected at one end to contact b of receptacle R (I: would then not be con nected to ground) and at its other end to contact 35 of switch 36. -in this modification, when the filament batterybecame 'too weak, the alarm B would sound.

When the foregoing device is mounted on a crane and the antenna approaches an energizeclpower line, theinput to the tube 28 will be such as to reduce the space current flowing therein to a value which cannot maintain coil 32 in energized condition. This will cause the alarmbellB'to ring. 7 V

The distance or range at which the alarm will sound can be preset by means of sliding contact 29.

The control may use standard inexpensive batteries having a life exceeding six months under normal 8 hour day operation.

The following values of components have been found to give satisfactory results:

, In the modified form of the invention disclosed in Fig. 3, the apparatus utilizes, instead of the two tubes 22 and 28, a double complex tube 40 including a highgain amplifier triode section 22a, handling the function of tetrode 22 of Fig. l, and -a control triode section 28a, handling the function of the tetrode 28 of Fig. '1. These triode sections have filaments Hand 42, coupled in series through a filament current limiting resistor 43 to the main lead 44 from direct current source .A+ (e. g. 6 .volts input'). High voltage (e. g.60 volts) is applied to plates -27 and 34 of the respective triodesections, from ahigh voltage connection 45 through branch conductors '45 and 47, the former being connected to plate 27 through resistor 26, and the latter being connected to plate-34 through the energizing coil 32 ofjrelay 33, whereby the plate current of control section 28a is utilized for actuating relay 33. The :plate 27 of amplifier 22a is coupled to control grid 39 of control triode 28:: through the couplingorblo'cking capacitor 29, whereby the voltage of' plate 27 isimpr'es'sed-upon grid 3%, to control the output of control tube -28a to relay energizing coil 32. Grid 30 is connected to ground through gri'd bias resistor 31. V V

Antenna 144s connected to the sweep arm 20 of gaincontrol potentiometer 48 whichis manually adjustable to control the response of amplifier 22a to radiant energy received by antenna 14, through the variations in the grid bias of grid 2-1 -of-'amplifier 22a. Grid 21 is connected to antenna 14, the potentiometer48 providing a variable grid leak connection to ground through a fixed resistance 49. The resistor 49 provides a fixed lower limit of control for a high gain rate phase of operation. A low gain rate phase of operation is provided for by a highdow switch 50, which provides a shunt connection to ground through a resistor 51 which is preferably, though not necessarily, of the same resistance value as resistor 49. Closing of switch places resistor "51 in shunting relation to resistor 49, reducing the sum value of the resistance in the circuit'to a value lowerth'an that of resistor 49, and leaving potentiometer 48 in control at a lower gain rate. V

The output-of control triode 28a is taken from plate 34 to'the energizing-coil 32 of relay 33 for actuating the latter "toward open position, the relay returning to its normally closed position wheneversai'd output is reduced below aminimum value for-maintaining the relay open.

Relay 33 has its fixed contact connected to the low voltage, bell ringing current supply conductor 44, and its movable contact is connected to one side of an alarm bell 52, and to contact a of connector R (from which' there is a connection through mating connector P, to the bell B). It is also connected to ground through an arc suppressor condenser 53 which functions to protect the contacts of relay 33 against pitting, and also to avoid radiation from the relay and bells, such'as would cause an undesired reception in the antenna circuit.

Bell 52 is preferably incorporated in the control unit, while bell B is located externally, as-inFig. 2,' f'er instance.

Connections of alarm bell B and interlock switch 13 to connector P are the same as in Fig. land the same reference numerals are used to designate the same. Connections of receptacle Rte relay 33 {contact a to the moving switch arm thereof and contact (I to the energizing coil 32), are the same and connections of contact b to ground is the same. 'Contact'c is'connected to a. plate voltage supply coming from a non-synchronous vibrator or interrupter 55 the output of which is fed into the primary of a step-up transformer 56. The output of transformer 56 is fed through arectifier 57 and a filter network 58 which converts the output into a steady applied -B+ voltage. Voltage is carried to the high voltage conductor through connections c, 0', through interlock switch 18, and thence through connections d, d.

An arc-suppressor condenser 59 is shunted across vibrator 55. A butter condenser 60 is shunted across the secondary of transformer56. lt-functions tocut off the peaks of the sine waves of the alternating current delivered from transformer 56, so as to reduce the maximum voltage thereof to a value safely below the breakdown limit of rectifier 57, 'the excess voltage being bypassed to ground.

The primary of transformer 56 is connected .on one side to-low voltagepower supply connector 46 and on its other side to vibratorSS, which provides an interrupting connection to ground, such thatpulses of the low voltage supply current areset up-in the transformerpn'rnaryQinducing a high voltage alternating currentin the'secondary.

A power indicator light 61 isconnected between power source A+ and ground. When light 61 is illuminated, adequate power is indicated. When light '61 dims or goes out, it indicates power drop to an inadequate level.

A satisfactory combination of resistance and capacity values for the various parts of the circuit, to achieve the desiredresults (for 6 volts input and 60 volt plate current values) is as follows: a

The connection of the contacts'a, b, c, 'd'of connector R'to-corresponding contacts a, b, c, ti of connector P, when the connectors arejoined together, are indicated'by the dotted lines a", b",-'c d"'respectively,'for facilitating'the 'readin-g'of the-circuit of Fig. '3.

I claim:

-1. An automatic approach alarm comprising'in combination a relay, said relay'having normally closed contacts, an electronic tube, the 'coilof 'saidrelaybein'gconneeted in the plate-cathode circuito'f said electronic tube whereby when current fiows throughsaid tube said relay will be energized and said contacts will be open, an

alarm device, a source of voltage for operating said alarm device, said alarm device being connected in series with said voltage source and said relay contacts whereby when said relay contacts are closed said alarm device will be operative, an antenna, an electronic amplifier, said antenna being connected to the input of said amplifier, means to couple the output of said amplifier to said electronic tube whereby when the antenna detects the presence of a radiation emitting object the current through the electronic tube will decrease,'the relay will become deenergized, the relay contacts will close, and the alarm device will operate, an antenna lead-in wire, said wire being connected at one end to said antenna, a normally open antenna interlock switch, a spring for urging said switch into open position, an operating lever for said switch, said antenna lead-in wire being connected at one point to said lever whereby to maintain said switch in closed position, the contacts of said antenna interlock switch being connected in series with the relay coil and the plate voltage supply for said electronic tube whereby when said lead-in wire will break intermediate said switch and said antenna said switch will open, said 'relay will become deenergized, said relay contacts will close, and said alarm device will operate.

2. An automatic approach alarm according to claim 1, including a filament supply battery for the electronic tube and the amplifier tubes which is separate from the source of voltage for operating said alarm device, whereby when said filament supply battery becomes weak the alarm device will operate.

3. An alarm for giving a warning when the boom of a crane approaches closer than a predetermined distance to an energized power line including a bell, a relay, said relay having normally closed contacts, an electronic tube, the coil of said relay being connected in the plate-cathode circuit of said electronic tube whereby when current flows through said tube said relay will be energized and said contacts will be open, a source of voltage for operating said bell, said bell having a connection in series with said voltage source and said relay contacts whereby said bell will be operative when said relay contacts are closed, an antenna on said boom, an electronic amplifier, said antenna being connected to the input of said amplifier, means to couple the input of said amplifier to said electronic tube whereby when the antenna approaches closer to the power line than a predetermined distance the bell will be energized, an antenna lead-in wire, said wire being connected at one end to said antenna, a normally open antenna interlock switch, a spring for urging said switch into open position, an operating lever for said switch, said antenna lead-in wire being connected at one point to said 'lever whereby to maintain said switch in closed position, the contacts of said antenna interlock switch being connected in series with the relay coil and the plate voltage supply for said electronic tube whereby when said lead-in wire will break intermediate said switch and said antenna said switch will open, said relay will become deenergized, said relay contacts will close, and said alarm device will operate, a resistor, said antenna being connected to said resistor, a sliding contact on said resistor, said sliding contact being connected to the input of said amplifier whereby to permit the distance between said antenna and the radiating object at which the alarm device will operate to be preset.

4. An alarm for giving a warning when the boom of a crane approaches closer than a predetermined distance to an energized power line including a bell having an energizing circuit including a power source and a relay, normally closed for completing said circuit and actuating said bell: electronic gain mechanism including a high-gain amplifier section and a control section, each of said sections including an electron-emitting filament, a plate, and a grid for controlling electron flow from the filament to the plate,

and means, including a blocking capacitor, coupling the grid of said control section to the plate circuit of said amplifier section so as to control the bias on said control section grid, said relay having an energizing coil in the plate circuit of said control section adapted normally to be energized by current flow in said plate flow so as to maintain said relay open and said bell inoperative; an antenna on said boom, connected to the control grid of said amplifier section so as to vary the bias of said grid in response to power reception by said antenna from a power line upon approach to a point within a predetermined distance therefrom, and to resultantly vary the bias on the grid of said control section, in a manner to reduce the current fiow to said relay to a value insufiicient to maintain the relay energized to open position, whereupon the relay will close and said bell will be actuated, an antenna lead-in wire, said wire being connected at one end to said antenna, a normally open antenna interlock switch, a spring for urging said switch into open position, an operating lever for said switch, said antenna lead-in wire being connected at one point to said lever whereby to maintain said switch in closed position, the contacts of said antenna interlock switch being connected in series with the relay coil and the plate voltage supply for said electronic tube whereby when said lead-in wire will break intermediate said switch and said antenna said switch will open, said relay will become deenergized, said relay contacts will close, and said alarm device will operate, a resistor, said antenna being connected to said resistor, a sliding contact on said resistor, said sliding contact being connected to the input of said amplifier whereby to permit the distance between said antenna and the radiating object at which the alarm device will operate to be preset.

5. An alarm for giving a warning when the boom of a crane approaches closer than a predetermined distance to an energized power line including an audible indicator device having an energizing circuit including a power source and a relay, normally closed for completing said circuit and actuating said bell: electronic gain mechanism including an amplifier section and a control section, each of said sections including an electron-emitting filament, a plate, and a grid for controlling electron flow from the filament to the plate, and means, coupling the grid of said control section to the plate circuit of said amplifier section so as to control the bias on said control section grid, said relay having an energizing coil in the plate circuit of said control section adapted normally to be energized by current flow in said plate flow so as to maintain said relay open and said bell inoperative; an antenna on said boom, connected to the control grid of said amplifier section so as to vary the bias of said grid in response to power reception by said antenna from a power line upon approach to a point within a predetermined distance therefrom, and to resultantly vary the bias on the grid of said control section, in a manner to reduce the current flow to said relay to a value insufiicient to maintain the relay enengized to open position, whereupon the relay will close and said bell will be actuated, an antenna lead-in wire, said wire being connected at one end to said antenna, a normally open antenna interlock switch, a spring for urging said switch into open position, an operating lever for said switch, said antenna lead-in wire being connected at one point to said lever whereby to maintain said switch in closed position, the contacts of said antenna interlock switch being connected in series with the relay coil and the plate voltage supply for said electronic tube whereby when said lead-in wire will break intermediate said switch and "said antenna said switch will open, said relay will become deenergized, said relay contacts will close, and said alarm device will operate, a resistor, said antenna being connected to said resistor, a sliding contact on said resistor, said sliding contact being connected to the input of said amplifier whereby to permit the distance between said antenna and the radiat- 7 ing obiect at which the alarm device will operate to be preset. i

6. An alarm as defined nrclaim 4 wherein said amplifier section and control section each consists ina separate ten-ode tube.

7. An alarm device as defined in claim 5,. wherein said amplifier section and control section are triode sections 7 and are both embodied in a complex tube having 21 C011!- through saidsecond fixed resistance, including a switch adapted when closed, to establish said direct. connection in shunting relation to said first mentioned fixed resistance and resistor, whereby toreduce the sum resistance of the twofixed resistances to a value below the minimum established by said: first mentioned fixed resistance. r

References- (lited in the file of this patent UNITED STATES PATENTS 2,009,447 Hart July so, 1935 2,107,525 Derby -s Feb. s, 1938 2,575,627 Johnson Nov. 20, 1951 2,615,969 Albrecht Oct. 28, 1952 FOREIGN PATENTS Switzerland Jan. 16, 1947 

